A known fastening system such a drainage system in a fruit press is shown in longitudinal section in FIG. 1. This system includes a multitude of drainage assemblies 3 disposed in a pressing chamber 2 one boundary of which is defined by a pressing plate 1. Only one of these assemblies is shown. It includes an elastic drainage core 4, via whose external grooves 5 (shown in FIG. 1A) the fluid is conducted out of the pressing chamber 2 during the pressing process, and a sock-shaped filter 6 for solid-fluid separation. The filter 6 is stretched over the core 2. The ends of the drainage core and the filter 6 are fastened in a core retainer 7. The filter 6 is guided via an elastic sleeve 8 and fixed with an O-ring 9. A disk 10 serves to support the sleeve 8 against a lateral pin 11, which is thrust crosswise into bores of the drainage core 4 and the core retainer 7, fixing the elements 4 and 7 to each other both axially and radially.
The core retainer 7 is connected to the pressing plate 1 with the aid of a distance bush 12 and a snap ring 13. A cam 14 of the snap ring 13, which engages in a groove 16 of the core retainer 7 by means of a slit 15 in the distance bush 12, cooperates with a collar 17 on the distance bush behind the plate 1 to secure the parts against axial sliding.
As shown in FIG. 1, during the pressing process, the drainage core 4 is bent sharply upstream of where it is clamped in the pressing plate 1. The disadvantage this known type of filter--and drainage core fastening is primarily that due to mechanical stress, the filter is damaged in the abrasion zones 18 and 19. This occurs in abrasion zone 18 by clamping the filter 6 between the drainage core 4 and the sleeve 8 and in abrasion zone 19 by filter abrasion as a result of pulling the filter 6 over the sleeve 8.
The sharp bending of the drainage core 4 also shortens its service life and partly hinders the discharge of fluid through the grooves 5 of the drainage core 4. The problem is the bending of the grooves 5, which are disposed on the circumference of the drainage core 4, due to compressive stresses which occur and which are symbolized in FIG. 1 by the character .sigma.. The cross section reduction of the grooves 5 resulting from this hinders the discharge of fluid and increases the danger of stoppage by means of deposited solid matter.